A successful spray drying operation depends upon the
techniques used for product recovery and emission control.
The choices can impact the product yield, classification of product,
product integrity, energy consumption, and environmental compliance.
portion of the product is collected from the spray dryer
to prevent particle degradation when product is friable.
when isolation of the larger particle size cut is desired.
another collection point, which increases capital and
efficiency largely dependent upon product density and
particle size distribution.
A generally low cost method of collecting up to 98% of product.
Useful when potential product contamination from multiple products exist.
Little maintenance required.
Relatively low fan energy consumption with pressure drop of 5-10 inches w.c.
Requires back up with bag filter or wet scrubber for emission control.
Can cause degradation of friable spray dried
Bag House Collection
Relatively low fan energy consumption with pressure drop of 3-6 inches w.c.
Can be used for single component product collection and particulate emission control with efficiencies up to 99.99% for most products.
Useful for friable products to prevent particle degradation.
Used downstream of cyclone for emission control when no liquid effluent is desired.
Moderate maintenance costs.
Not good for "sticky" powders.
Wet Scrubber Collection
Typically a venturi type is used.
High efficiencies possible (up to 99% @ 1.5 micron).
Requires recycle or treatment of liquid effluent.
Relatively low maintenance.
Relatively high fan energy consumption with pressure drop of 15-30 inches w.c.
Higher level of instrumentation can be required for density and level control.
Used after particulate is removed and chemical vapors, such as HCl, need to be scrubbed.
Can also be used to recover heat from dryer discharge to produce hot water for use elsewhere in the facility.
Higher level of instrumentation usually required to control density, level, pH, and/or temperature.